<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <!-- 内部样式表 -->
    <style>
        div {
            width: 100px;
            height: 100px;
            background: blue;
        }
    </style>

    <!-- 外部样式表 -->
    <link rel="stylesheet" href="./04.css">
</head>
<body>
    <!-- 内联样式 -->
    <!-- <div style="width:100px;height:100px;background:red;"></div> -->

    <div></div>

    <span>this is my test text</span>
</body>
</html>